CN114039176A

CN114039176A - Dual-band frequency-adjustable microstrip band-pass filter

Info

Publication number: CN114039176A
Application number: CN202111112514.2A
Authority: CN
Inventors: 许卫; 朱接印; 李宏斌; 雷禾兴; 李凯; 方涵; 陈雨阳; 颜海轮
Original assignee: Wuhan Binhu Electronic Co ltd
Current assignee: Wuhan Binhu Electronic Co ltd
Priority date: 2021-09-23
Filing date: 2021-09-23
Publication date: 2022-02-11

Abstract

The invention relates to the field of microwaves, in particular to a micro-strip band-pass filter with adjustable dual-band frequency. The circuit layer comprises a left circuit layer and a right circuit layer, and the left circuit layer is in a vertically symmetrical structure except for a port I; the right circuit layer is obtained by rotating the left circuit layer by 180 degrees by taking the origin of coordinates as a center, the X axis of a coordinate system is positioned on the horizontal central line of the left circuit layer, and the distance between the Y axis and the left circuit layer is 0.285 mm. The invention optimizes the impedance matching by changing the position of the feed point, greatly improves the insertion loss index, and can adjust the working frequency of the filter by changing the capacitance value.

Description

Dual-band frequency-adjustable microstrip band-pass filter

Technical Field

The invention relates to the field of microwaves, in particular to a micro-strip band-pass filter with adjustable dual-band frequency, which can be applied to the fields of mobile phones, electronic tags and the like.

Background

The filter is an important component of a wireless communication system, the performance of the filter is directly related to the whole communication system, and the filter is required to have good loss characteristic and high frequency selectivity. The general microstrip band-pass filter has only one working frequency band and can meet the use requirements of conventional communication products.

However, with the continuous development of electronic technology, the application of dual-band technology is increasing (such as electronic tags, mobile phone antennas, dual-band radar, etc.), and therefore, a need is raised for a dual-band microstrip band-pass filter. By looking up data, some existing designs of dual-band microstrip band-pass filters generally have insertion loss of 0.5dB to 1.5dB and minimum volume of 20.2mm × 14mm × 0.8 mm. In order to meet the higher and higher index requirements of a communication system on a microstrip filter, it is particularly important to design a high-performance and miniaturized two-band microstrip filter.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a micro-strip band-pass filter with adjustable dual-band frequency. The invention adopts a design method of a half-wavelength stepped impedance resonator, optimizes impedance matching by changing the position of a feed point, improves the insertion loss index, and changes the working frequency of the filter by adjusting the power length of a resonance branch. The invention reduces the insertion loss to below 0.4 dB.

The technical scheme of the invention is as follows: a miniature low-loss microstrip band-pass filter with adjustable two-band frequency comprises a dielectric layer, a circuit layer, a bottom circuit layer and a bottom layer distributed on two sides of the dielectric layer.

The method is characterized in that: the circuit layer includes left circuit layer, right circuit layer, and the size of each leg of left circuit layer is as shown in the table:

location numbering	Size (mm)	Location numbering	Size (mm)
				x1	1.4	y3	2.18
x2	0.75	y4	1.54
				x3	6.1	y5	1.42
x4	3.15	y6	1.73
				x5	1.6	y7	1.76
y1	6.15	d1	0.57
				y2	2

Except for the port I, the left circuit layer is in a vertically symmetrical structure; the right circuit layer is obtained by rotating the left circuit layer by 180 degrees by taking the origin of coordinates as a center, the X axis of a coordinate system is positioned on the horizontal central line of the left circuit layer, and the distance between the Y axis and the left circuit layer is 0.285 mm. The length of the resonant stub y2 is directly related to the filter operating frequency.

According to the miniaturized low-loss microstrip band-pass filter with adjustable two-band frequency, the miniaturized low-loss microstrip band-pass filter is characterized in that: the whole rectangular area of the dielectric layer is filled with a medium, the material of the filled medium is PTFE Ceramic, the dielectric constant is 10.2, and the thickness is 0.8 mm.

According to the miniaturized low-loss microstrip band-pass filter with adjustable two-band frequency, the miniaturized low-loss microstrip band-pass filter is characterized in that: the circuit layer is covered with copper foil, the surface of the copper foil is plated with gold, the thickness of the copper foil is 0.035mm, and the thickness of the gold-plated layer is not less than 0.2 um.

According to the miniaturized low-loss microstrip band-pass filter with adjustable two-band frequency, the miniaturized low-loss microstrip band-pass filter is characterized in that: the bottom layer is covered with copper foil, the surface of the copper foil is plated with gold, the thickness of the copper foil is 0.035mm, and the thickness of the gold-plated layer is not less than 0.2 um.

The invention has the beneficial effects that: 1. the filter has two working frequency bands, is adjustable in frequency, has extremely low insertion loss and has flexible frequency selectivity. The invention has higher inhibition effect at frequencies outside two working frequency bands. 2. The circuit structure of the invention is simple, is convenient for batch production, and has low requirement on manufacturing precision. 3. The structure size is small, and the method can be applied to the fields of mobile phones, electronic tags and the like.

Drawings

Fig. 1 is a front view of a filter circuit board.

FIG. 2 is a schematic view of a dielectric layer.

Fig. 3 side view of a filter circuit board.

Fig. 4 filter insertion loss performance curves.

Fig. 5 filter standing wave performance curves.

FIG. 6 is a three-dimensional model diagram of a filter circuit board.

Description of reference numerals: dielectric layer 1, circuit layer 2, bottom layer 3, capacitor C1.

Detailed Description

The invention is further illustrated below with reference to the figures and examples.

Fig. 1 and 3 are a front view and a side view of the filter, respectively, in which fig. 1 shows a dielectric layer 1 as the whole area included in the outer frame, fig. 3 shows a circuit layer 2 and a bottom layer 3 as black filled portions, and the circuit layer 2 and the bottom layer 3 are disposed on both sides of the dielectric layer 1. The circuit layer 2 of the invention is covered with copper foil and the surface of the copper foil is plated with gold, the thickness of the copper foil is 0.035mm, the thickness of the gold-plated layer is not less than 0.2um, the bottom layer 3 is covered with the copper foil completely and the surface of the copper foil is plated with gold, and the thickness is consistent with the circuit layer 2.

Fig. 2 is a schematic diagram of a dielectric layer 1, in which the entire rectangular region is filled with a dielectric material of PTFE Ceramic, the dielectric constant is 10.2, and the thickness is 0.8 mm.

As shown in fig. 1, the circuit layer 2 of the present invention includes a left circuit layer and a right circuit layer, and the size of each stub of the left circuit layer is shown in table 1. From the structure, if the rectangular area of the first port is not considered, the left circuit layer is in a vertically symmetrical structure, the left circuit layer is integrally in an E structure, a square grounding point is arranged on the inner side of the E structure, and the square grounding point is connected with the E structure through a capacitor C1. The right circuit layer is obtained by rotating the left circuit layer by 180 degrees by taking the origin of coordinates as a center, the X axis of a coordinate system is positioned on the horizontal central line of the left circuit layer, and the distance between the Y axis and the left circuit layer is 0.285 mm. The port of the left circuit layer is a port one, and the port of the right circuit layer is a port two. The first port and the second port are input/output ports of the filter, and the two ports can be used interchangeably. The first port can be connected with a power amplifier, and the second port can be connected with a microwave transmitting device.

The dimensions of each bar are shown in table 1:

TABLE 1

As shown in fig. 1, capacitor C1 is soldered to circuit layer 2, and by changing the capacitance value, the length of resonant branch y2, which is related to the resonant frequency of the filter, is changed, which can shift the operating frequency of the filter. The capacitance value of the capacitor is adjusted within the range of 1-10 pF, so that the working frequency of the filter can deviate about 100 MHz. The same printed board can be used, the filter can adapt to different working frequencies only by adjusting the capacitor, and the circuit complexity is reduced.

Fig. 4 and 5 show the filter-related performance indexes of the C1 with capacitance values of 2pF, 3pF, 4pF and 5pF, respectively.

The device has small integral structure size of 16mm multiplied by 12mm multiplied by 0.87mm, can be applied to the fields of electronic tags, mobile phone antennas and the like, and realizes convenient and high-performance communication. The device is obtained through testing, the insertion loss of the device in the two working frequency bands is respectively less than 0.37dB and 0.25dB, and the frequency adjustable function is realized. Typical operating frequency ranges are the S-band and C-band.

The present invention is not limited to the above embodiments, and those skilled in the art can implement the present invention in other various embodiments according to the disclosure of the present invention, so that all designs and concepts of the present invention can be changed or modified without departing from the scope of the present invention.

Claims

1. A microstrip band-pass filter with adjustable dual-band frequency comprises a dielectric layer, a circuit layer and a bottom circuit layer, wherein the circuit layer and the bottom circuit layer are distributed on two sides of the dielectric layer.

Except for the first port and the second port, the left circuit layer is of a vertically symmetrical structure; the left circuit layer overall layer E structure is provided with a square grounding point at the inner side, and the square grounding point is connected with the E structure through a capacitor; the right circuit layer is obtained by rotating the left circuit layer by 180 degrees by taking the origin of coordinates as a center, the X axis of a coordinate system is positioned on the horizontal central line of the left circuit layer, and the distance between the Y axis and the left circuit layer is 0.285 mm.

2. The dual band frequency tunable microstrip bandpass filter of claim 1 wherein: the circuit layer is covered with copper foil, the surface of the copper foil is plated with gold, the thickness of the copper foil is 0.035mm, and the thickness of the gold-plated layer is not less than 0.2 um.

3. The dual band frequency tunable microstrip bandpass filter of claim 1 wherein: the capacitance value of the capacitor can be adjusted within the range of 1-10 pF, and the capacitance values of the four adjusted capacitors are the same.

4. A dual band frequency tunable microstrip bandpass filter according to any one of claims 1 to 3 wherein: the whole rectangular area of the dielectric layer is filled with a medium, the material of the filled medium is PTFECERAMIC, the dielectric constant is 10.2, and the thickness is 0.8 mm.

5. A dual band frequency tunable microstrip bandpass filter according to any one of claims 1 to 3 wherein: the bottom layer is covered with copper foil, the surface of the copper foil is plated with gold, the thickness of the copper foil is 0.035mm, and the thickness of the gold-plated layer is not less than 0.2 um.